Irreversible processes and the accelerated-decelerated phases of the Universe

A model for the Universe is proposed where it is considered as a mixture of scalar and matter fields. The particle production is due to an irreversible transfer of energy from the gravitational field to the matter field and represented by a non-equilibrium pressure. This model can simulate three distinct periods of the Universe: (a) an accelerated epoch where the energy density of the scalar field prevails over the matter field, (b) a past decelerated period where the energy density of the matter field becomes more predominant than the scalar energy density, and (c) a present acceleration phase where the scalar energy density overcomes the energy density of the matter field.Comment: 6 pages, 2 figures, to be published in Brazilian Journal of Physic

Spontaneous CP Violation in the Next-to-Minimal Supersymmetric Standard Model Revisited

We re-examine spontaneous CP violation at the tree level in the context of the next-to-minimal supersymmetric standard model (NMSSM) with two Higgs doublets and a gauge singlet field. We analyse the most general Higgs potential without a discrete Z_3 symmetry, and derive an upper bound on the mass of the lightest neutral Higgs boson consistent with present experimental data. We investigate, in particular, its dependence on the admixture and CP-violating phase of the gauge singlet field, as well as on tan(beta). To assess the viability of the spontaneous CP violation scenario, we estimate epsilon_K by applying the mass insertion approximation. We find that a non-trivial flavour structure in the soft-breaking A terms is required to account for the observed CP violation in the neutral kaon sector. Furthermore, combining the minimisation conditions for spontaneous CP violation with the constraints coming from K0-K0bar mixing, we find that the upper bound on the lightest Higgs-boson mass becomes stronger. We also point out that the electric dipole moments of electron and neutron are a serious challenge for SUSY models with spontaneous CP violation.Comment: 19 pages, LaTeX2e, 5 figures; matches the published versio

The ionizing sources of luminous compact HII regions in the RCW106 and RCW122 clouds

Given the rarity of young O star candidates, compact HII regions embedded in dense molecular cores continue to serve as potential sites to peer into the details of high-mass star formation. To uncover the ionizing sources of the most luminous and compact HII regions embedded in the RCW106 and RCW122 giant molecular clouds, known to be relatively nearby (2-4 kpc) and isolated, thus providing an opportunity to examine spatial scales of a few hundred to a thousand AU in size. High spatial resolution (0.3"), mid-infrared spectra (R=350), including the fine structure lines [ArIII] and [NeII], were obtained for four luminous compact HII regions, embedded inside the dense cores within the RCW106 and RCW122 molecular cloud complexes. At this resolution, these targets reveal point-like sources surrounded by nebulosity of different morphologies, uncovering details at spatial dimensions of <1000AU. The point-like sources display [ArIII] and [NeII] lines - the ratios of which are used to estimate the temperature of the embedded sources. The derived temperatures are indicative of mid-late O type objects for all the sources with [ArIII] emission. Previously known characteristics of these targets from the literature, including evidence of disk or accretion suggest that the identified sources may grow more to become early-type O stars by the end of the star formation process

High Resolution 4.7 um Keck/NIRSPEC Spectra of Protostars. I: Ices and Infalling Gas in the Disk of L1489 IRS

We explore the infrared M band (4.7 um) spectrum of the class I protostar L1489 IRS in the Taurus Molecular Cloud. This is the highest resolution wide coverage spectrum at this wavelength of a low mass protostar observed to date (R=25,000; Dv=12 km/s). Many narrow absorption lines of gas phase 12CO, 13CO, and C18O are detected, as well as a prominent band of solid 12CO. The gas phase 12CO lines have red shifted absorption wings (up to 100 km/s), likely originating from warm disk material falling toward the central object. The isotopes and the 12CO line wings are successfully fitted with a contracting disk model of this evolutionary transitional object (Hogerheijde 2001). This shows that the inward motions seen in millimeter wave emission lines continue to within ~0.1 AU from the star. The colder parts of the disk are traced by the prominent CO ice band. The band profile results from CO in 'polar' ices (CO mixed with H2O), and CO in 'apolar' ices. At the high spectral resolution, the 'apolar' component is, for the first time, resolved into two distinct components, likely due to pure CO and CO mixed with CO2, O2 and/or N2. The ices have probably experienced thermal processing in the upper disk layer traced by our pencil absorption beam: much of the volatile 'apolar' ices has evaporated and the depletion factor of CO onto grains is remarkably low (~7%). This study shows that high spectral resolution 4.7 um observations provide important and unique information on the dynamics and structure of protostellar disks and the evolution of ices in these disks.Comment: 11 pages, 6 figures Scheduled to appear in ApJ 568 n2, 1 April 200

The Environment and Nature of the Class I Protostar Elias 29: Molecular Gas Observations and the Location of Ices

A (sub-)millimeter line and continuum study of the Class I protostar Elias 29 in the ρ Ophiuchi molecular cloud is presented whose goals are to understand the nature of this source and to locate the ices that are abundantly present along this line of sight. Within 15"-60" beams, several different components contribute to the line emission. Two different foreground clouds are detected, an envelope/disk system and a dense ridge of HCO^+-rich material. The latter two components are spatially separated in millimeter interferometer maps. We analyze the envelope/disk system by using inside-out collapse and flared disk models. The disk is in a relatively face-on orientation (<60°), which explains many of the remarkable observational features of Elias 29, such as its flat spectral energy distribution, its brightness in the near-infrared, the extended components found in speckle interferometry observations, and its high-velocity molecular outflow. It cannot account for the ices seen along the line of sight, however. A small fraction of the ices is present in a (remnant) envelope of mass 0.12-0.33 M_☉, but most of the ices (~70%) are present in cool (T < 40 K) quiescent foreground clouds. This explains the observed absence of thermally processed ices (crystallized H_2O) toward Elias 29. Nevertheless, the temperatures could be sufficiently high to account for the low abundance of apolar (CO, N_2, O_2) ices. This work shows that it is crucial to obtain spectrally and spatially resolved information from single-dish and interferometric molecular gas observations in order to determine the nature of protostars and to interpret Infrared Space Observatory and future Space Infrared Telescope Facility observations of ices and silicates along a pencil beam

Caracterização antigênica de tripomastigotas metacíclicos de Trypanosoma cruzi provenientes do vetor e de cultura

Metacyclic trypomastigotes ol the CL strain of Trypanosoma cruzi obtained from triatomid vectors and from axenic cultures were comparatively analysed as to their antigen make-up and immunogenic characteristics. They were found to be similar by the various parameters examined. Thus, sera of mice immunized with either one of the two metacyclic types precipitated a 82Kd surface protein from 131I-labeled culture metacyclics. Sera of mice protected against acute T. cruzi infection by immunization with killed culture metacyclics of a different strain (G) recognized, by immunoblotting, a 77Kd protein in both types of CL strain metacyclics. A monoclonal antibody raised against G strain metacyclics, and specific for metacyclic stages of this strain, reacted with both CL strain metacyclic types. Both metacyclic forms were similarly Iysed by various anti-T. cruzi sera, in a complement-mediated reaction.Tripomastigotas metacíclicos da cepa CL de Trypanosoma cruzi, originários de triatomineos e de cultura axênica, foram comparativamente analisados quanto a sua composição antigênica e características ímunogênicas. Os vários parâmetros examinados mostraram que as duas formas metacíclicas sáo semelhantes. Assim, soros de camundongos imunizados com qualquer uma das formas metacíclicas precipitaram uma proteína de superfície de 82Kd de tripomastigotas metacíclicos de cultura marcados com 131I. Soros de camundongos protegidos con trn infecção aguda por T. cruzi, por imunização com formas metacíclicas de cultura inativadas, de uma cepa diferente (G), detectaram por imunoblotting uma proteína de 77Kd em ambas as formas metacíclicas da cepa CL. Um anticorpo monoclonal, produzido contra as for mas metaciclicas da cepa G, e específico para tripomastigotas metacíclicos, reagiu com formas metacíclicas da cepa CL tanto do vetor quanto de cultura. As duas formas metacíclicas mostraram suscetibilidade semelhante à lise por vários soros anti-T. cruzi, em uma reação mediada por complemento

Alterações nos atributos físicos do solo em decorrência da manipulação de resíduos da vegetação secundária.

O objetivo do estudo é verificar as alterações ocorridas nos atributos físicos do solo em decorrência da manipulação de resíduos de vegetação secundária em relação à queima, a fim de propor manejos alternativos e de maior sustentabilidade ao sistema vigente

Charcoal (Biochar) as soil conditioner to enhance fertilizers and water use efficiency in agriculture in acid tropical soils in the Central Amazon Basin

This article summarize result of many experiments conducted in 15 years of research with biochar in nursery and field experiments in the Central Amazon